In a bowl, combine flour, salt, and sugar.
Dissolve yeast in warm water and let it sit for 5 minutes.
Add the yeast mixture and olive oil to the flour mixture.
Knead the dough for about 5-7 minutes until smooth.
Cover the dough and let it rise in a warm place for 1 hour.
Preheat the oven to 425°F (220°C).
Roll out the dough into circles (about 8 inches in diameter).
Spread ricotta cheese on one half of each circle.
Add mozzarella and pepperoni on top of the ricotta.
Fold the dough over to create a half-moon shape and seal the edges.
Place calzones on a baking sheet and bake for 15-20 minutes until golden brown.
Serve hot with marinara sauce for dipping.